Q. $m_{p}\ $and $m_{n}$are masses of proton and neutron respectively. An element of mass $M$ has $Z$ protons and $N$ neutrons then
A) $M\ > Zm_{p}\ + \ Nm_{n}$
B) $M = \ \ Zm_{p}\ + \ Nm_{n}$
C) $M\ < Zm_{p}\ + \ Nm_{n}$
D) $M$ may be greater than less than or equal to $Zm_{p}\ + \ Nm_{n},$depending on nature of element
Explanation
(c) When a nucleus is formed, then the mass of nucleus is slightly less than the sum of the mass of $Z\ $protons and $N$ neutrons.
$ie,\ \ \ \ \ \ M < (Zm_{p}\ + Nm_{n})$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.